People in Ireland stored their butter in bogs for at least 3,500 years, leaving behind well-preserved waxy globs with a very pungent odor. In a recent study, researchers dated 32 globs of bog butter at National Museum of Ireland from about 1700 B.C. to the 17th century. They even say the practice of storing butter in cool-temperature bogs may have continued into the early 20th century.
Peat bogs in northwest Europe are known for their preservation abilities. Researchers have found over a thousand eerily-preserved human bodies in these European bogs, as well as hundreds of butter globs in Irish and Scottish bogs. Most of the museum’s 32 Irish bog butters are made from milk fat, and stored in containers made from materials like animal bladders, animal hides and wood.
The bogs likely kept butter in an edible state for centuries, and preserved the butter as an artifact for much longer. “Theoretically the stuff is still edible—but we wouldn’t say it’s advisable,” said the museum’s Andy Halpin to The Irish Times in 2016.
Ancient people didn’t necessarily put butter in a bog to keep it fresh for eating later, the way people today might put butter in a fridge (even though modern salted butter lasts months without refrigeration). It’s also possible they stored it there because butter had some special cultural or religious significance. Just as researchers have suggested that bog bodies were human sacrifices, some have also suggested that bog butters were religious offerings.
“It is unlikely there was a single reason for the deposition of bog butter over four millennia,” says the University College Dublin’s Jessica Smyth, lead author of the new study published in Scientific Reports, in a university press release. “In certain periods they may have been votive deposits, while at other points in time it may have been more about storage and even protection of valuable resources.”
Smyth’s study notes that “early medieval Irish law tracts list butter as one of the products payable as food rents.” If you left your rent butter out too long, you might unintentionally liquidate your assets, so it would make sense to deposit it in a bog.
“Foods are an often-ignored category but may have also been infused with symbolism,” Smyth said. “In this regard, it may be no coincidence that both butter and gold are commonly deposited in bogs.”